The present invention relates to an aqueous dispersed solution of a substituted succinic anhydride and a process for producing the same. More particularly, the present invention relates to such an aqueous dispersion of a substituted succinic anhydride used as a sizing agent having excellent sizing effect in paper making steps and exhibiting excellent operations even in a dilute stability and a process for producing the same.
There is known a sizing paper employing aqueous dispersed solution of a substituted succininc anhydride, and various types of aqueous dispersions have been heretofore proposed.
For example, an aqueous dispersion prepared by mixing an aqueous solution of cationic starch and a substituted succinic anhydride by a strong mechanical agitation in a homogeneous state (disclosed in Japanese Patent Publication No. 2305/1964 official gazette), an aqueous dispersion prepared by dispersing a substituted succinic anhydride in water or an aqueous solution of specific aqueous soluble polymer substance with the aid of a selected surfactant (disclosed in Japanese Patent Publication No. 36044/1978 official gazette, Japanese Patent Laid-open No. 45731/1983 official gazette, Japanese Patent Laid-open No. 47498/1984 official gazette), and further an aqueous dispersion prepared by dispersing a substituted alkyl-substituted or alkenyl-substituted succinic anhydride or a mixture (a) of the succinic anhydrides which contain 70 to 99.9 percent by weight and a mixture (b) of polyoxyethylene alkyl-ether phosphoric acid ester, polyoxyethylene alkylaryl ether phosphoric acid ester or the mixture of these phosphoric acid esters which contain 0.1 to 30 percent by weight in water with the aid of an aqueous solution of aqueous soluble polymer compound (disclosed in Japanese Patent Application No. 134051/1983).
However, in the abovementioned aqueous dispersion employing the former cationic starch of the aqueous dispersions of the substituted succinic anhydrides, a considerably large apparatus is not only required to disperse the substituted succinic anhydride in water, but it is difficult to sufficiently pulverize the aqueous dispersed solution thus obtained into fine dispersion particles, and the resultant dispersion has such a disadvantage that the dispersion cannot avoid the slight decrease in the sizing performance.
In the above-described aqueous dispersion employing the latter mixture of the aid, the prepared mixture loses its stability in presveration and cannot secure a sufficient dispersibility of the substituted succinic anhydride in water, and the resultant aqueous dispersion not only loses its sizing effect with the lapse of time after preparation but deteriorates in the dispersibility of the substituted succinic anhydride having an internal olefin structure adapted for a sizing agent in water.
Further, the aqueous dispersion utilizing the substituted-alkyl succinic anhydride or substituted-alkenyl succinic anhydride or the mixture of both has been proposed to have excellent properties for a preservation stability as the disadvantage of the mixture of the air of the substituted succinic anhydride of light and the surfactant in the mixture prepared by dispersing a substituted alkyl-substituted or alkenyl-substituted succinic anhydride or a mixture (a) of the succinic anhydrides which contain 70 to 99.9 percent by weight and a mixture (b) of polyoxyethylene alkyl-ether phosphoric acid ester, polyoxyethylene alkylaryl ether phosphoric acid ester or the mixture of these phosphoric acid esters which contain 0.1 to 30 percent by weight in water with the aid of an aqueous solution of aqueous soluble polymer compound, and the resultant aqueous dispersion further provides preferable dispersibility in water for the substituted succinic anhydride having an internal olefin structure as a sizing agent as its merits, but when the aqueous dispersion obtained from this mixture is used as a sizing agent in an industrial scale, some problems are still retained. In other words, the aqueous dispersion of the substituted succinic anhydride obtained from the mixture proposed in Japanese Patent Application No. 134051/1983 exhibits dilute stability of the aqueous dispersion in case that the cationic starch dissolved in water of continuous state is contained in the aqueous dispersion, but, in other case, causes insufficient dilute stability, and when this aqueous dispersion is employed as a sizing agent in the practical paper making process, the dispersion has such a drawback that it contaminates the wires, rolls and carpets of the paper making machine and cannot operate continuously for a long period of time.
If the mixture is dispersed in the aqueous solution dissolved with the cationic starch in advance when preparing the aqueous dispersion from the abovementioned mixture in this case, the aqueous dispersed solution having preferable dilute stability can be prepared, but the aqueous solution of the cationic starch itself is unstable in an ageing manner, and the cationic starch should be dissolved in water immediately before using the aqueous dispersion as a sizing agent as well as the dispersibility of the substituted succinic anhydride of the starch in water is small. Thus, a negative factor that a strong or large-scale emulsifying apparatus for preparing the aqueous dispersion is indispensably required.